1. Field of the Invention
The present invention relates to a liquid ejection head, and more particularly, to technology for a liquid ejection head which ejects liquid onto a liquid receiving medium.
2. Description of the Related Art
An inkjet recording apparatus having an inkjet type of ejection head forms a desired image on a medium by ejecting ink from a plurality of nozzles provided in the ejection head. In recent years, there have been demands for improved quality of the printed image and higher printing speed in inkjet recording apparatuses. In order to meet these demands, it is necessary to reduce the size of the dots which compose the image and to increase the density of the dots. In order to reduce the dot size, the amount of ink ejected in each ejection action should be reduced by reducing the diameter of the nozzles provided in the print head. Furthermore, in order to form the dots at a high density, the nozzle arrangement inside the print head should be set to a high density.
In order to achieve finer nozzles and higher nozzle density in a print head in this way, a micro-processing technique such as etching is used, or a laminated structure is adopted in which cavity plates processed by means of a micro-processing technique are layered together. In this way, nozzles for ejecting ink, liquid chambers for accommodating ink to be ejected from the nozzles, ink flow channels, and the like, can be formed finely and accurately in a print head.
In the inkjet print head described in Japanese Patent Application Publication No. 2003-512211, in a print head in which an ink supply layer formed by a porous member which supplies ink to pressure chambers is positioned between a nozzle layer in which nozzles are formed and a cavity layer in which ink cavities (pressure chambers) are formed, piezoelectric elements are disposed on a displacement plate (diaphragm) which constitutes the ceiling of the ink cavities, wiring members are provided from the piezoelectric elements in a direction substantially perpendicular to the nozzle surface, and a substrate (wiring layer) is provided at the end of the wiring members.
However, if the nozzles of an ejection head having the structure described above are formed to a high density, then problems of the following kinds arise, and therefore, in practice, it is difficult to increase the density of the nozzles and to eject ink with good efficiency, with a structure of this kind.
For example, in the case of a structure where, taking the pressure plate (displacement plate, diaphragm) forming one face of the pressure chambers as a boundary, the pressure chambers, supply side flow channels (common liquid chamber, supply ports), and the nozzles are formed on one side of the pressure plate, and actuators such as piezoelectric elements are disposed on the opposite side of the pressure plate. In this case, if the density of the nozzles is increased, then the supply side flow channels become smaller, and if it is sought to eject ink by driving a plurality of nozzles at a high frequency (at a short ejection cycle), then the ink supply to the pressure chambers cannot keep up with demand. Therefore, if the supply side flow channels are increased in size in order to achieve a smooth supply of ink, the distance from the pressure chambers to the nozzles becomes greater and ejection becomes more difficult to perform. Layout restrictions of this kind relating to the size of the supply side flow channels make it difficult to set a high ejection frequency.
Furthermore, if the number of nozzles provided in the ejection head is increased in order to achieve a high nozzle density, the number of actuators and the number of actuator wires also increase accordingly. This makes it difficult to dispose (pattern) the wires onto the same surface (for example, the pressurization plate on which the piezoelectric elements are positioned) as in the related art.
In the inkjet print head described in Japanese Patent Application Publication No. 2003-512211, since piezoelectric elements, conductive bonding elements, a printed substrate mounted with a driver chip, and the like, are provided between the ink supply layer and the ink manifold which accumulates ink to be supplied to the ink supply layer, then the ink flow channel from the ink manifold to the ink supply layer is long. Thus, as the density of the nozzles becomes increased, and there is a possibility that the ink supply from the ink manifold to the nozzles will not be able to meet demand.